Houston's crime lab has been reeling for some time from the discovery of numerous convictions tainted by false lab reports. It's about to get worse:

Six independent forensic scientists, in a report to be filed in a Houston state court today, said that a crime laboratory official - because he either lacked basic knowledge of blood typing or gave false testimony - helped convict an innocent man of rape in 1987. The panel concluded that crime laboratory officials might have offered "similarly false and scientifically unsound" reports and testimony in other cases, and it called for a comprehensive audit spanning decades to re-examine the results of a broad array of rudimentary tests on blood, semen and other bodily fluids.

How many cases are affected in this new probe?

Elizabeth A. Johnson, a former director of the DNA laboratory at the Harris County medical examiner's office in Houston, said the task would be daunting. "A conservative number would probably be 5,000 to 10,000 cases," Dr. Johnson said. "If you add in hair, it's off the board."

Barry Scheck, one of Mr. Rodriguez's lawyers, said that Harris County was the worst place in America for a crime laboratory scandal. "We know already that they couldn't do DNA testing properly," Mr. Scheck said. "Now we have a scandal that calls into question many thousands more cases. And this jurisdiction has produced more executions than any other county in America." Since the death penalty was reinstated in 1976, Texas has executed 323 people, 73 for crimes in Harris County.

The first scandal was bad enough:

A state audit of the crime laboratory, completed in December 2002, has found that DNA technicians there misinterpreted data, were poorly trained and kept shoddy records. In many cases, the technicians used up all available evidence, making it impossible for defense experts to refute or verify their results. Even the laboratory's building was a mess, with a leaky roof contaminating evidence. The DNA unit was shut down soon afterward, and it remains closed.